As a valve opening and closing timing control device, a technique including a torsion spring for biasing a driven-side rotating body with respect to a driving-side rotating body in an advancing direction is disclosed (for example, JP11-132014A (Reference 1) and JP2013-185459A (Reference 2)).
In the valve opening and closing timing control device of Reference 1, a torsion spring is disposed between a front plate of the driving-side rotating body and the driven-side rotating body. A posture of the torsion spring is stabilized by forming a spiral groove on a contact surface of the front plate being that is in contact with the torsion spring along a winding angle of a first turn of the torsion spring.
In the valve opening and closing timing control device of Reference 2, a bottomed cylindrical bush exposed on a front surface side of the driving-side rotating body is fixed to the driven-side rotating body and the torsion spring is housed in the bush. An end portion of the torsion spring extends radially outside and is engaged with a pin-like hook fixed to the front plate. In addition, a plurality of ribs protruding radially inside the bush are provided and the ribs abut against the torsion spring. Therefore, a posture of the torsion spring is corrected such that a center axis of the torsion spring and a rotational axis of the driven-side rotating body are parallel to each other.
In the valve opening and closing timing control device of Reference 1, it is possible to stabilize the posture of the torsion spring by forming the spiral groove on the front plate, but processing is complicated and there is room for improvement.
In addition, as in Reference 2, if the configuration, in which the plurality of ribs are provided radially inside the bush, is provided, when the torsion spring is contracted in diameter, there is a concern that the torsion spring may be inclined in a direction of the rotational axis until abutting against the ribs. As a result, the driving-side rotating body and the driven-side rotating body will be relatively inclined and thereby smooth relative rotation inhibited and device performance decreased. In addition, strength is required for the hook and the front plate, and a size of the device is likely to be increased so as not to move the pin-like hook with which the end portion of the torsion spring is engaged.